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CONTRIBUTIONS OF THE THROWING ARM AND TRUNK MOTIONS TO GENERATE THE RAPID ELBOW EXTENSION MOTION DURING BASEBALL PITCHING
Poster 293, Poster Session 2/Sport. 14:10-15:10, Room 103 & Alley Area
S766
CONTRIBUTIONS OF THE THROWING ARM AND TRUNK MOTIONS TO GENERATE THE RAPID ELBOW EXTENSION MOTION DURING BASEBALL PITCHING K. Naito and T. Maruyama Department of Human System Science, Tokyo Institute of Technology, Tokyo, JAPAN; email : [email protected] INTRODUCTION The proximal to distal joint sequential motion of the throwing arm, especially the rapid elbow extension that occurs in the acceleration phase, is a common feature in skillful pitching movement. Some studies [1,2] have examined the mechanism that generates the rapid elbow extension in baseball pitching and have suggested that it must result from the motion-dependent interactions of other joint rotations and not from the action of the elbow extensor [2]. However, these analyses dealt with the two-kinetic chain using the simple throwing arm model, and the question of which joint motions - including the trunk, upper arm, forearm and hand - primarily interact and generate the elbow extension is still to be determined. The purpose of this study was to determine the contributions of the muscular torques of the throwing arm joints and motion-dependent interactions due to the throwing arm joint and trunk rotations to produce maximum elbow extension angular velocity. METHODS The throwing motions of three baseball players were recorded using high-speed cameras set to film at 250fps. Reflective markers were attached to the throwing arm and trunk in order to identify the joint centers of the shoulder, elbow, wrist and trunk. The trunk rotational angles and anatomical joint angles of the throwing arm were calculated by Euler angle convention. The joint torques (muscular torques) of the shoulder, elbow and wrist were calculated using inverse dynamics. In this study, we developed a throwing arm dynamical model including 7 DOF of the throwing arm joints (shoulder horizontal adductionabduction, adduction-abduction, external-internal rotation, elbow extension-flexion, wrist ulnar-radial deviation, flexion-extension and supination-pronation) and 3 DOF rotational axes of the trunk (counter-clockwise-clockwise rotation about the spinal axis, medial-lateral lean and anterior-posterior lean) in order to calculate the motiondependent interaction torques due to the trunk and throwing arm joint motions. This model was used to decompose the maximum elbow extension angular velocity during baseball pitching into 7 components due to throwing arm muscular torques, and 24 components due to motion-dependent interaction torques caused by the angular velocity and gyroscopic angular acceleration of the throwing arm joints and trunk, gravity-dependent component and external force (exerted by a ball)-dependent component. The contributions were defined by the ratio of the maximum elbow extension angular velocity and causal components due to the muscularand motion-dependent moments of the trunk, shoulder, elbow and wrist joints. RESULTS AND DISCUSSION The mean ball speed was 33.7±1.1m/s, as measured by a radar gun. The mean maximum elbow extension angular velocity was 37.9±3.2rad/s. From the analysis of the mean values of all contributions, it was shown that the trunk Journal of Biomechanics 40(S2)
Figure 1: The typical patterns of the elbow extensionflexion angular velocity and its muscular torque- and motion-dependent components.
counter-clockwise (CCW) angular velocity-dependent component was the main contributor (63.4%). In addition, the shoulder horizontal adduction (HAD) angular velocitydependent component was the second contributor (33.6%). On the other hand, the total contribution of the throwing arm muscular torque-dependent components was a negative value (-44.9%). In particular, the elbow flexion torque(–37.5%) and HAD torque- (-33.8%) dependent components were shown as large negative values. These results indicate that the rapid elbow extension during baseball pitching was almost entirely generated by the angular velocity-dependent interactions due to CCW and HAD rotations, and not from the muscular torques of the trunk and throwing arm joints (Figure 1). This fact does not support the concept, presented by the previous study [2], that the reversing muscular torques at the proximal joints (trunk and shoulder) is advantageous in causing the rapid distal joint (elbow) motion and enhancing ball speed. CONCLUSIONS The rapid elbow extension during baseball pitching is determined by the motion-dependent interactions between the trunk counter-clockwise rotation and shoulder horizontal adduction angular velocities. To increase the elbow extension motion, a baseball pitcher should control the combination of the joint angles and angular velocities of the throwing arm and trunk rather than muscle actions. REFERENCES 1. Feltner ME. Int J Sport Biomech 5, 420-450, 1989. 2. Herring RM, et al. J Biomech 25, 1173-1184, 1992.
XXI ISB Congress, Poster Sessions, Thursday 5 July 2007
S766
CONTRIBUTIONS OF THE THROWING ARM AND TRUNK MOTIONS TO GENERATE THE RAPID ELBOW EXTENSION MOTION DURING BASEBALL PITCHING K. Naito and T. Maruyama Department of Human System Science, Tokyo Institute of Technology, Tokyo, JAPAN; email : [email protected] INTRODUCTION The proximal to distal joint sequential motion of the throwing arm, especially the rapid elbow extension that occurs in the acceleration phase, is a common feature in skillful pitching movement. Some studies [1,2] have examined the mechanism that generates the rapid elbow extension in baseball pitching and have suggested that it must result from the motion-dependent interactions of other joint rotations and not from the action of the elbow extensor [2]. However, these analyses dealt with the two-kinetic chain using the simple throwing arm model, and the question of which joint motions - including the trunk, upper arm, forearm and hand - primarily interact and generate the elbow extension is still to be determined. The purpose of this study was to determine the contributions of the muscular torques of the throwing arm joints and motion-dependent interactions due to the throwing arm joint and trunk rotations to produce maximum elbow extension angular velocity. METHODS The throwing motions of three baseball players were recorded using high-speed cameras set to film at 250fps. Reflective markers were attached to the throwing arm and trunk in order to identify the joint centers of the shoulder, elbow, wrist and trunk. The trunk rotational angles and anatomical joint angles of the throwing arm were calculated by Euler angle convention. The joint torques (muscular torques) of the shoulder, elbow and wrist were calculated using inverse dynamics. In this study, we developed a throwing arm dynamical model including 7 DOF of the throwing arm joints (shoulder horizontal adductionabduction, adduction-abduction, external-internal rotation, elbow extension-flexion, wrist ulnar-radial deviation, flexion-extension and supination-pronation) and 3 DOF rotational axes of the trunk (counter-clockwise-clockwise rotation about the spinal axis, medial-lateral lean and anterior-posterior lean) in order to calculate the motiondependent interaction torques due to the trunk and throwing arm joint motions. This model was used to decompose the maximum elbow extension angular velocity during baseball pitching into 7 components due to throwing arm muscular torques, and 24 components due to motion-dependent interaction torques caused by the angular velocity and gyroscopic angular acceleration of the throwing arm joints and trunk, gravity-dependent component and external force (exerted by a ball)-dependent component. The contributions were defined by the ratio of the maximum elbow extension angular velocity and causal components due to the muscularand motion-dependent moments of the trunk, shoulder, elbow and wrist joints. RESULTS AND DISCUSSION The mean ball speed was 33.7±1.1m/s, as measured by a radar gun. The mean maximum elbow extension angular velocity was 37.9±3.2rad/s. From the analysis of the mean values of all contributions, it was shown that the trunk Journal of Biomechanics 40(S2)
Figure 1: The typical patterns of the elbow extensionflexion angular velocity and its muscular torque- and motion-dependent components.
counter-clockwise (CCW) angular velocity-dependent component was the main contributor (63.4%). In addition, the shoulder horizontal adduction (HAD) angular velocitydependent component was the second contributor (33.6%). On the other hand, the total contribution of the throwing arm muscular torque-dependent components was a negative value (-44.9%). In particular, the elbow flexion torque(–37.5%) and HAD torque- (-33.8%) dependent components were shown as large negative values. These results indicate that the rapid elbow extension during baseball pitching was almost entirely generated by the angular velocity-dependent interactions due to CCW and HAD rotations, and not from the muscular torques of the trunk and throwing arm joints (Figure 1). This fact does not support the concept, presented by the previous study [2], that the reversing muscular torques at the proximal joints (trunk and shoulder) is advantageous in causing the rapid distal joint (elbow) motion and enhancing ball speed. CONCLUSIONS The rapid elbow extension during baseball pitching is determined by the motion-dependent interactions between the trunk counter-clockwise rotation and shoulder horizontal adduction angular velocities. To increase the elbow extension motion, a baseball pitcher should control the combination of the joint angles and angular velocities of the throwing arm and trunk rather than muscle actions. REFERENCES 1. Feltner ME. Int J Sport Biomech 5, 420-450, 1989. 2. Herring RM, et al. J Biomech 25, 1173-1184, 1992.
XXI ISB Congress, Poster Sessions, Thursday 5 July 2007